Alarm system



I/w i F. L.. LEMM El" AL ALARM SYSTEM Original Filed Jan. l0, 1956 Aug. 2, 1960 :PCEM1 Tl QN.

United States Patent ALARM SYSTEM Frederick L. Lemm and Richard H. Jewens, Houston, Tex., assignors, by direct and mesne assignments, to Information Systems, Inc., Skokie, Ill., a corporation of Illinois Continuation of application Ser. No. 558,218, Jan. 10, 1956. This application Jan. 8, 1957, Ser. No. 633,159

13 Claims. (Cl. 340-213) t This is a continuation of application Serial No. 558,218, led January 10, 1956, now abandoned for an Alarm System.

This invention relates to annunciator or alarm systems, and particularly to an electrical alarm system having visual and audible alarm means for initially `signalling the failure or abnormal condition of a point being monitored.

In the interest of safety and eiciency, it has become common practice to provide at a central location in industrial plants a panel board containing a maze of alarm lamps associated with various points in the plant to be monitored. When the point being monitored reaches an abnormal state, a sensing device associated with such point energizes the circuit controlling the light in question and also an audible alarm for attracting the atten- :tion of an operator to the panel board where he can immediately identify the location of the fault in question. The reliability of such a system, of course, is a function of the reliability of the alarm system itself and it, accordingly, becomes desirable to provide a means for signalling a fault in the alarm system through visual and audible means in the same general way as the alarm system signals the abnormal condition of the point or points being monitored. f

It is, accordingly, one of the objects of the present invention to provide an alarm system with provision forgiving preferably both a visual and audible alarm signalling failure of components of the alarm system of a distinguishing character from the alarm given when a point being monitored becomes abnormal, preferably both with and without failure of the components so that the operator may at substantially all times have knowledge of the operating condition of the alarm system as well as the points being alarm light for signalling the abnormal condition of each point to be monitored and a trouble light which signals the burning ont of any of the relays, and also most preferably of the alarm light as well.

A nother object of the invention is to provide an alarm system as above described wherein the size, complexity and cost of the alarm apparatus associated with each point to 'oe monitored is not substantially different from apparatus heretofore available without the self-failure signalling features above outlined.

Another object of the invention is to` provide an alarm system as above described having means for testing the condition of the trouble light. A related object of the invention is to provide an alarm system having a test switch` and a trouble or test light which upon depression of the test switch will light up if substantially all components of the associated alarm circuit are in operating condition.

Still another object of thepresent invention is to provide an alarm system as above described which automaii cally sets into operation a stand-by means which substitutes Ifor the unit or device being monitored as such unit or device becomes inoperative.

A still further object of the present invention is to provide an alarm system as above described which, in addition to the centrally located audible alarm above mentioned, includes a second audible alarm located at the situs of the point being monitored.

In accordance with a preferred form of the invention, in the case where there are two control relays per point or alarm light, one to be referred to as an alarm relay and the other as an acknowledgment relay, both relays are operated in a normally-energized condition and the alarm light is connected in series with one of the relays, preferably lbut not necessarily the acknowledgment relay. The latter relay is designed to operate normally in series with the alarm light, and the alarm light is substantially deenergized or in dim condition during normal operation of the system. The alarm relay is associated with a set of sensor contacts, preferably in series with a Inormally closed set of sensor contacts, which sensor contacts are controlled by a fault-detecting unit, such as a therrnocouple, located at the point being monitored. The alarm light is controlled by contacts of the alarm relay so that upon operation of the sensor contacts to their trouble-indicating position, the alarm relay will be de-energized and the alarm light will be energized, that is, it will light brightly. The relay with which the alarm light is not directly associated is provided with a set of contacts connected preferably in series with the relay which is directly associated with the alarm light so that the latter relay will be de-energized whenever the former relay is de-energized. The trouble light is associated with the sensor contacts, preferably in series therewith, and with a set of contacts controlled by one of the relays. The circuit is such that whenever either of said relays are de-energized while the movable sensor contact is in its normal position, the trouble light will light brightly thereby signalling most probably a burned out relay or a burned out alarm light, since the relay in series with the alarm light is de-energized where it is burned out, or the other relay or the alarm lamp is burned out. When the alarm relay is de-energized for any reason, its contacts controlling the alarm light will cause the latter to be energized.

An acknowledgment switch is associated with the acknowledgment relay so that upon operation of the acknowledgment switch the audible can be silenced as long as the `acknowledgment relay is then operative.

In the case where the alarm light is in series with the acknowledgement relay, the audible alarm is controlled by a set of normally-closed contacts of the acknowledgement relay sothat the audible alarm will be sounded when the acknowledgement relay becomes de-energized due to any of the above-mentioned circuit faults. An acknowledgement switch is provided which, in cooperation with holding contacts of such relay, re-energize the acknowledgement relay when operated, except where the fault exists in the energization circuit thereof, so as to silence the audible alarm.

With the circuit arangement above described, if bo the alarm light and trouble light are brightly lighted, then the operator knows that the fault is not with the point being monitored but in the energization circuit of the alarm relay, most probably the burning out of the alarm relay. And if only the trouble light is lit, then the voperator knows that the trouble is in the'energization circuit of the acknowledgement relay, most probably the burning out of the acknowledgement relay or the alarm light. `In the latter situation, the replacement of the alarm light willirnmediately indicate the cause of the fault. If the audible alarm sounds and both the trouble and alarm lights are dark, the operator then knows that t'hesignal light-has burned out and the point being monitored is abnormal.

To test the operation of the trouble light, the trouble light is arranged in a branch circuit preferably includinga normally-open test switch, normally-'open contacts of the relayinseries with the alarm light, and the sensor contactsso that during normal operation of the sensor contacts and the relays, depression ofthe test switch will light the trouble light if the light is in operating order. In effect, the lighting of the trouble light under these circumstances indicates that the relays and the sensor contacts are in their normal operating conditions.

'Other objects, advantages and features of the invention will become apparent upon making reference to the specification to follow, the claims and the drawings wherein:

' Fig. l is a schematic diagram of the most preferred form of the invention; and

Fig. 2 is a chart illustrating some of the various light and horn sequences with the present-invention.

Fig. -l shows a schematic diagram of an alarm circuit for monitoring a single point or variable. A conditionresponsive unit, not shown, such as a thermocouple located at the situs of the point or variable being monitored, controls a preferably normally-closed sensor switch 8 which opens when the condition of the point reaches an abnormal condition. The switch 8 is electrically connected by a cable g to a central monitoring point in the plant involved where a large panel board, not shown, is provided containing signal lights, such as light S, for all the points in the plant being monitored. Control circuits to be described are provided for each sensor switch so that upon opening or anysensor switch, the associated signal light will be lighted and a common audible alarm horn H-l is sounded to attract the operators attention to the panel board where the location of the fault can immediately be determined by noting the lighted signal lamp.

For the most part, all of the electrical apparatus exelusive to a particular signal lamp are assembled together as an integral unit generally indicated lby the reference numeral 10, there being similar such units associated with other signal Alights or sensor switches. The unit may be enclosed in a casing and provided with a socket J into which a plug may be inserted containing terminals for making all connections to the unit 10. The arrows in Fig. l represent plug and socket connections for the unit 1t). 'Ille unit-10 may carry the alarm light S, and, in accordance with the present invention, a trouble or test light T. The alarm unit 10 also hasa push button switch assembly mounted on the exterior thereof including push button switches SW- and SW-2. The switches are ganged together so that depression of one switch will automatically depress the other.

The lightS, which will be sometimes referred to as an alarm light, is arranged to be normally dimly lighted and to -be brightly lighted when the associated sensor switch 8 opens to thereby signal an abnormal condition of the point being monitored thereby. The ytrouble light T is arranged to be automatically lighted brightly whenever any of the relays to be described in the alarm unit l or their associated circuits become open due, for example, to the burning out ofthe relay coils, or whenever the signal or alarm lamp S burns out. Simultaneously with the lighting of either the alarm light S` or lthe trouble light T, the audible alarm H-l is sounded to attract the attention of lthe operator to the panel board. In a manner to be explained, the push button switch S'W-Z acts as a test switch and if the Vtest light T lights upon depression of. the push button switch then this indicates that the trouble light is operating properly and also that the relay coils of the unit are in normal operating-condition.

The operation of the push button switch `SW-l, in the absence of any circuit failure in alarm .unit 10, is used as anaeknowledgement switch by theoperator to silence the audible alarm H-l when the alarm light S is initially lighted upon opening of the sensor switch 8. In case of circuit failure in the alarm unit 10, depression of the push button switch SW-l will have various effects depending upon the particular part of the circuit which is operating abnormally. Inthe preferred form of the invention illustrated in Fig. l, the energization circuits of the various relays to be described arenormally closed or energized and the circuit fault to be monitored by the trouble light T is the open circuiting of such circuits in the presence of the closure of the sensor switch 8, which is a normally closed switch in the embodiment of the invention being described.

Electrical energy for operating -the alarm unit isjprovided by any suitable-direct current or alternating current power source 12 .from which extend power lines Pl-PZ. .Power l-ine 4P2 connects with the alarm unit through the plug and socket terminal connection 1 and power line Pil connects to the alarm unit 10 Vdirectly through the plug and socket terminals 3, although most of the circuits of the alarm nnit l0 connect with the power line P1 through other units located externally of .the alarm unit l0, such as the sensor switch 8 and the audible alarm H-1. However, all of the circuits of the alarm -unit iti connect directly with the pow-er line P2 and the extension of this line within the alarm unit 10 has been identified .by the reference character P2.

yEach alarm unit 10, only one being shown in Fig. '1, includes a pair of relays M and A -to be referred to respectively as the alarm relay and the acknowledgement relay. The alarm relay M is connected in a circuit extending from the power line B2. and through relay coil M, plug and socket terminals 2 and the sensor switch 8 leading to the .power line P1. Since the sensor switch is a normally closed switch, the alarm relay will be normally energized.

In describing the position of the contacts of the relays of the alarm unit 10, the terms normally-closed or normally-open will represent the condition of the contacts in `question during the de-energized state of the `associated relays. Thus, a set of contacts which are normally closed will be open during the energized state of the relay controlling the same. Also, the contacts of the relays will :be identified by a capital letter corresponding to the letter used to identify the relay coil controlling the same together With a number which -dstinguishes the contact in question from other contacts of the same relay. Additionally, the positions of the contacts shown in Fig. l represent the normalrpositions thereof, that is their lposition during the de-energized state of the associated relay coils.

The acknowledgement relay coil A is in a circuit extending from the power line P2 and through thevlarnent of the alarm or signal light S, .the normally-open section of a Vsingle-pole double throw switch comprising movable contact M-Z .and stationary contacts M-Z and M412", relay coil A, a parallel vcircuit including normally-open holding contacts A-5 of the acknowledgement relay A in parallel with Inormally-open contacts M-3 of .the alarm relay M, and plug yand socket terminals 3 which connect with the power line 'PL The acknowledgement relay coil A is designed to operate in series with or in parallel with the signal light S. The alarm or signal lamp S normally receives a small amount of current through .the circuit including the relay coil A so that the light bur-ns dimly. However, when the alarm relay M is in a Vde-energized state, the alarm light S is directly Vconnected to the power line Pl so as 'to burn brightly by means, of a branch 14 connected in parallel with the relay A and its holding contacts A-S, which branch includes a normally-closed set of contacts M-S which are closed under the condition in question to couple the full line voltage te the alarm light S. Y

Upon the de-energization of the alarm relay colM due, :for example, tov ,the opening of the sensor switch 8 or to the .burning .out of the coil M, the acknowledgef fj ment relay A is also de-energized due to the movement of the movable contact M2 of the above-mentioned single pole double-throw switch from the stationary contact M-2 to the stationary contact M-Z, the latter being connected to a line 16 extending directly to the power line yP2'. Before the movable contact M-Z' reaches the stationary contact M- the relay coil A is de-energized so that itsholding contacts A-S are open. When the movable contact M-Z' reaches the stationary contact M-2", the acknowledgement relay A remains cie-energized because at that moment its holding contacts are open and `the contacts M-3 in parallel therewith are open because of the de-energized condition of the alarm relay. This does not eifect the lighting of the alarm light S because of the above-mentioned parallel branch 14.

In the `de-energized state of the acknowledgement relay A, an energization circuit for the audible alarm H-1 is completed through a set of normally-closed contacts A-l of the -acknowledgment relay which contacts are in a branch extending from the power line P2' and through the contacts A-1, plug and socket terminals 4 and the audible alarm H-1 leading to the power line P1. Depression of the push button switch SVV-1, which is connected in parallel rwith the holding contacts A-S of the acknowledgement relay, will re-energize the acknowledgement relay A which will lock-in through its holding contacts A-S thereby silencing the audible alarm H-l lupon the consequent opening of the normally-closed contacts A-1. The alarm light S remains lighted as long as the alarm relay M remains de-energized. If the alarm light S was lighted' because of the open condition of the sensor switch S, upon closure of the sensor switch 8 the `alarm relay M will become re-energized and the alarm light S will become de-energized, that is become dimly lighted.

As above explained, the trouble (or test) light T iS provided to signal the burning out of the relay coils M or A or the alarm light S. The trouble light T is in a circuit extending from the power line PZ and through the @lament of this light, a set of normally-closed contacts A-Z of acknowledgement relay A, plug and socket terminals 5, line 16 and the sensor switch 8 leading to the power line P1. Thus, trouble light T will light when the acknowledgement relay A is deenergized which, as above explained, occurs if the alarm relay M is deenergized, if the acknowledgement relay coil A burns out,` or Iif the alarm -light S burns out, in the presence of a closed condition of a sensor switch S. The audible alarm H-1 will simultaneously sound upon the lighting of the trouble light T since the normally-.closed contacts A-1 associated with the audible alarm will then be closed. If the sensor switch is in its abnormal open position and the A relay burns out, then the trouble light T will be out and the alarm light will be on. If depression of the switch SW-l does not silence the horn, then the operator knows that the acknowledgement relay has burned out and that the point -being monitored is abnormal.

If the 4fault which caused the trouble light T to light was the burning out of the alarm relay coil M, then the consequent closure of the normallyclosed contacts M-S in the 'branch 14 leading to the alarm light S will cause the alarm light S also to light up. The alarm light S will not light up simultaneously with the trouble light T if the fault was the burning out of the A relay coil or the alarm light S itself. Also, if the audible alarm sounds .and both the alarm and trouble lights are out7 this indicates that .the alarm light is burned out and the point being monitored is abnormal.

Depression of the push button switch SW-1, upon the occurrence of any of the above-mentioned circuit faults, will re-energize the acknowledgement relay A in all cases except a situation where the acknowledgement lrelay coil has burned out or an open circuit has developed in the energization circuit thereof, as for example, due to the burning out of the alarm light S. When the acknowledge- 6 ment relay A re-energizes, this'silences the audible alarm H-l. If the audible alarm H-l cannotbe silencedby depression of the push button switch SW-l, and the alarm light S is de-energized, then the operator has a further indication that the fault is probably in the burning out of the acknowledgement relay coil A or theV burn'- ing out of the alarm light S. Since the alarm light Scan be quickly replaced by a new alarm light, theoperator can quickly determine whether the fault is with the relay A or the alarm light S.

In order to test for the operation of the alarm light T, a push button switch SW-Zis connected in a test branch extending from the bottom terminal of the trouble light T and through the switch SW-Z to itself, a normally-` open set of contacts A-3 of the acknowledgment relay, plug and socket terminals S, and the normally-closed sensor switch 8. Therefore, if the depression of the-push button switch SW-Zresults in the lighting of the trouble or test light T, the operator knows that the trouble light T is operating properly, that the acknowledgement and alarm relay coils A and M are energized and' that th sensor switch 8 is closed. p

In order to alert a workman in the vicinity of the point being monitored of the abnormal condition of such point, an auxiliary emergency audible alarm or bell H-2 may be provided in the vicinity of the point being monitored which operates simultaneously with the above-mentioned audible alarm H-1. Accordingly, Vthe auxiliary audible alarm H-2 is located in a circuit extending from the power line P2' and through a set of normally-closed contacts A-4, plug and socket terminals 6 and the audible alarm H-Z leading to the power line P1.

If thepoint being monitored is a particularly critical point, makingdesirable the immediate substitution of a stand-by unit for the unit which has become defective, a stand-by unit 16 in Fig. l is associated with the alarm unit 10 so that it may be automatically inserted into the point of the system being monitored upon the existence of a fault at such point. Accordingly, the stand-by unit 16 includes an electrically controlled element (not shown) which is in an energization circuit extending from the power line P2 and through a set of normally-closed contacts M-1, plug and socket terminals 7 and the abovementioned control element of the stand-by unit 16 leading to the power line P1. Thus, when the sensor switch S opens the alarm relay M is accordingly de-energized, the normally-closed contacts M-1 will close to energize the control unit for the stand-by unit 16 which substitutes the stand-by unit for the defective unit.

The present invention has thus provided an alarm or annunciator system, which in addition to the normal alarm light, is provided with a trouble light which lights up when the relays burn out, and, most preferably, also when the alarm light burns out. Moreover, means are provided for testing for the proper operation of Athe trouble light in the form of a manual test switch. If depression of the test switch results in the lighting of the trouble light, the operator knows not only that the trouble light is operating but that the circuits associated with the relay coils in the circuit are energized as they should be. Furthermore, it indicates that the sensor switch 8 is closed. All of these advantages are obtained by means of a circuit which does not require additional relays over that acquired for a circuit not having such features, and the additional contacts and circuitry are such that the resultant unit can be made to sell for not too much more than a conventional system. i

Although the drawings show practically all of the sets of relay contacts as individual sets of contacts, it should be understood that, in accordance with the usual practice, contacts of the same relay are combined wherever possible into single-pole, double-throw units. This is the case,'for example, whenever two sets of contacts of the same relay have a common terminal connection and one set is normally-open and the other is normally closedl A The `term sensor used in the claims refers to a device including control means usually contacts, which is responsive to the condition of a variable being monitored by closing or opening such contacts whenever the variable ireaches a value which is considered actually or potentially abnormal, requiring the alerting of an operator.

It'should be understood that numerous modifications may be made of the most preferred formof the invention illustrated in the drawings without deviating from the broader aspects of the invention.

We claim as our invention:

1. In an alarmv unit including` at least two normally energized relaysrand `a visual alarm means connected in circuit withrar condition-responsive sensor switch means so that-operation of said sensor switch to a position indicating anv abnormal condition of the point being monitored will de-energize at least one of said relays and will operate the visual alarm means, the improvement comprising a visual trouble-indicating means, an energization circuit `for said trouble-indicating means including said sensor switch means, contacts of at least one of said relays, and circuit means connected to said troubleindicating means, sensor switch means and said contacts of said one relay for preventing energization of said trouble-indicating means by operation of said last-mentioned contacts when said sensor switch means is in its position indicating the abnormality of the point being monitored, land energizing said trouble-indicating means when either of said relays become de-energized and said sensor switch means is in its normal position, and audible alarm means for signalling an alarm condition to an operator when either said visual trouble-indicating means or said visual alarm means is energized.

2. In an alarm unit including normally energized relays which are all normally energized and a visual alarm means, one of the relays being connected in series with a. normally closed condition-responsive sensor switch means so that opening of said sensor switch will deenergize at least one relay and will operate the visual alarm means, the Vimprovement comprising a visual trouble-indicating means, an energization circuit for said troubleindicating means including said trouble-indicating means, normally closed contacts of .at least one of said relays and said sensor switch means `all being in mutual series relationship, Said sensor switch means being thus arranged toprevent energization of said trouble-indicating means by operation of said last-mentioned contacts when said sensor switch means is in its position indicating the abnormality of the point being monitored, said last-mentioned contacts and relays being arranged to energize said trouble-indicating means when either of said relays become de-energized and said sensor switch means is in its normal position, audible alarm means, and an energization circuit for said audible alarm including contacts of at least one of said relays arranged Vto sound said audible alarm means when any of said relays become deenergized under any condition of said sensor switch means. Y l 3. In an electrical alarmisystem including rst control means vwhich is energized during the normal operating conditions of the point being monitored, sensor means responsive to the abnormal condition ,of said point by effecting the de-energization of said tirst control means, second control means which is energized during the normal operating condition of said point, visual -aiarm means responsive to the (le-energization `ot said first kcontrol means for signalling the abnormal condition of said point, and audible alarm `means to 4be initially energized simultaneously with -said visual alarm means, the improvement comprising visualtrouble indicating means for signalling the burning out Yof any of said control means, means Vresponsive to the Vde-energization vof one of said control means for effecting ,the de-energization of the other of said control means, an energization circuit for said visualtrouble indicating means including means responsive to the de-energization of said other control means when the sensor` means is in its normal condition for energization said visual-trouble indicating means, and an energization circuit for said audible alarm including means responsive to the de-energization of said other control means for energizing the audible alarm.

4. In an electrical alarm system including irst control means which is energized during the normal operating conditions oi the point being momtored, sensor means responsive to the abnormal condition of said point by effecting the de-energization of said first control means, second control means which is energized during the normal operating condition of said point, visual alarm means responsive to the de-energization of said rst control means for signalling the abnormal condition of said point, and audible alarm means to be initially energized simultaneously with said visual alarm means, the improvement comprising visual-trouble indicating means for signalling the burning ont of any of said control means and said iirst visual alarm means, said visual-alarm means being connected in series circuit relationship with one of said control means, the latter control means being in an operable energized state when so connected in series with said visual alarm means but being normally de-energized when said Visual alarm means has burned out, said visual alarm means being normally in a substantially de-energized state when so operated in series with said control means, means responsive to the de-energization of the other of said control means for eecting the de-energization of said one control means, an energization circuit for said visual-trouble indicating means including means re* sponsive to the de-energization of said one control means when the sensor means is in its normal condition for energization said visual-trouble indicating means, and an energization circuit for said audible alarm including means responsive to the deaenergization of said one control means.

5. In an electrical alarm system including an alarm relay which is energized during the normal operating conditions of the point being monitored, sensor switch means responsive to the abnormal condition of said point by efecting the de-energization of said alarm relay, an acknowledgement relay which is energized during the normal operating condition of said point, manually operable acknowledgement switch means for changing the state of energization of said acknowledgement relay from the condition thereof when said sensor switch is in its abnormal-indicating position, visual alarm means responsive to the de-energization of said alarm relay for signalling the abnormal condition' of said point, and audible alarm means to be initially energized simultaneously with said visual alarm means and to be normally de-energized upon said operation of said acknowledgement switch means, the improvement comprising visual-trouble indicating means for signalling the burning out of any of said relays, means responsive to the de-energization of one of said relays for eiecting the cie-energization of the other of said relays, an energization circuit for said visual-trouble indicating means including means responsive to the deenergization of said other relay when the sensor switch means is in its Vnormal condition for energization said visual-trouble indicating means, and an energization circuit for said audible alarm including means responsive to the de-energization of said other relay for energizing the audible alarm, said acknowledgement switch means when operated dez-energizing said audible alarm except during failure of said acknowledgement relay. i

6. ln Ian electrical alarm system including an alarm relay which is energized during the normal operating conditions of the point being monitored, sensor switch means responsive to the abnormal condition of said point by eifecting the deenergization of said alarm relay, an acknowledgement relay which is energized `during the'normal operating condition of said point,`manually operable acknowledgement switch means for changing the state of energization of said acknowledgement relay from the condition thereof when said sensor switch is in its abnormal-indicating position, visual alarm means responsive to the de-energization of said alarm relay for signalling the abnormal condition of said point, and audible alarm means to be initially energized simultaneously with said visual alarm means and to be normally de-energized upon said operation of said acknowledgement switch means, the improvement comprising visual-trouble indicating means for signalling the burning out of lany of said relays and said 'visual alarm means, said visual alarm means being connected in series circuit relationship with one of said relays, the latter relay being in an operable energized state when so connected in series with said visual alarm means but being normally de-energized when said visual alarm means has burned out, the visual alarm means being normally in a substantially de-energized state when operated in series with said relay, means responsive to the de-energization of the other of said relays for effecting the de-energization of said one relay, an energization circuit for said visual-trouble indicating means including means responsive to the de-encrgization of said one relay when the sensor switch means is in its normal condition for energizing said visual trouble-indicating means, and an energization circuit for said audible alarm including means responsive to the de-energization of said one relay for energizing the audible alarm, said acknowledgement switch means when operated de-energizing said audible alarm except during failure of said alarm light or acknowledgement relay.

7. In an alarm unit including -at least two relays and a visual alarm means connected in circuit with a condition-responsive sensor switch means so that operation of said sensor switch to a position indicating an abnormal condition of the point being monitored will operate at least one of said relays and will energize the visual alarm means, the improvement comprising visual test means, an energization circuit for visual test means including said sensor switch means, a manually-operable test switch and contacts of at least one of said relays, a-nd circuit connecting for preventing energization of said visual test means by operation of said test switch and said last-mentioned contacts when said sensor switch means is in its position indicating the abnormality of the point being monitored, and said test switch and said last-mentioned contacts being arranged to operate said test means to indicate positively the proper normal operation of said relays as well as proper operation of said test means and the sensor switch means when the sensor switch means is in its normal position.

8. In an alarm unit including at least two normally energized relays and a visual alarm means connected in circuit with a normally closed condition-responsive sensor switch means so that opening of said sensor switch to a position indicating an abnormal condition of the point being monitored will de-energize at least one of said relays and will energize the visual alarm means, the improvement comprising visual test means, an energization circuit for said Visual test means including said sensor switch means, a normally-open manually-operable test switch and normally-open contacts of at least one of said relays all in series with one another, energization circuit including connection for preventing energization of said test means by operation of said test switch and said last-mentioned contacts when said sensor is in its position indicating the abnormality of the point being 9. In an alarm unit including at least two relays and a visual alarm means connected in circuit with a conditionresponsive sensor switch means so that operation of said sensor switch to a position indicating an abnormal condition of the point being monitored will operate at least one of said relays and will energize the Visual alarm means, the improvement comprising visual test means, an energization circuit for said visual test means including said sensor switch means, a manually-operable test switch and contacts of at least one of said relays, energization circuit including circuit connection for preventing energization of said test means by operation olf said test switch and said last-mentioned contacts when said sensor is in its position indicating the abnormality of the point being monitored, said test switch and said last-mentioned contacts being arranged to operate said test means to indicate positively the proper normal operation `of said relays aswell as proper operation of said test means and the sensor switch means when the sensor switch means is in its normal position, and a second energization circuit for said test light including said sensor switch means and contacts of at least one of said relays, said contacts being arranged to operate said test means to indicate the abnormal condition of either of said relays when said sensor switch means is in its normal position.

l0. An annunciator system comprising: a source of energizing potential, an alarm relay having sets of both normally-open and normally-closed contacts, an acknowledgement relay having sets of both normally-open and normally-closed contacts, a normally-closed sensor switch which opens when the variable to be monitored becomes abnormal, a normally-open acknowledgement switch, a normally-open test switch, an alarm light, a trouble-indicating light, means connecting said alarm relay and said sensor switch in series across saidsource of energizing potential, the alarm relay thereby being normally energized,4 an energization circuit for said acknowledgement relay between said acknowledgement relay and said source of energizing potential and including a parallel circuit arrangement of said acknowledgement switch, a set of normally-open contacts of said alarm relay and a set of normally-open contacts of said acknowledgement relay in series circuit relation with said acknowledgement relay, whereby closure of any of said-parallel connected elements will energize said acknowledgement relay, said er1- ergization circuit further including rst and second alternate branch circuits in series with said acknowledgement relay and said parallel circuit, one of said branch circuits including normally-open contacts of said alarm relay in series with said alarm light which, when the variable being monitored is abnormal, eifect Athe energization of theacknowledgement relay and the dim lighting of said alarm light, and, when said Variable is abnormal or said alarm light burns out, effect the de-energization of said acknowledgement relay, the other branch circuit including normally-closed contacts of said alarm relay effecting energization of the acknowledgement relay when an abnormal condition of the variable has been acknowledged by momentary closure of said normally-open acknowledgement switch, an energization circuit for said alarm light including normally-closed contacts controlled by said alarm relay which connects the alarm light to said source of energizing potential to light the same brightly when the alarm relay becomes de-energized as the variable being monitored becomes abnormal, an energization circuit for said trouble-indicating lightincluding said sensor switch, a set ofnormally-closed contacts of `said acknowledgement relay and circuit connections connecting said sensor switch, trouble-indicating light and saidlatter contacts to said source of energizing potential for lighting brightly t said trouble-indicating` light when the sensor switch is closed indicating a normal variable, and said acknowledgement relay is de-energized, and a test circuit connected in parallel with said normally-closed contacts of said acknowledgement relay comprising said normallyopen test switch and a'set of normally-open contacts of said acknowledgement relay, whereby the trouble-indicatinglight will also become energized upon closure of said test switch provided said acknowledgement relay is energized.

l1. An annunciator system comprising: a source of energizing potential, an alarm relay having sets of both normally-open and normally-closed contacts, an acknowledgement relay having sets of both normally-open and normally-closed contacts, a normally-closed sensor switch which opensV when the variable to be monitored becomes abnormal, a normally-open acknowledgement switch, an alarm light, a Vtrouble-indicating light, means connecting said alarm relay and said sensor switch in series across said source of energizing potential, the alarm relay thereby being normally energized, an energization circuit for said acknowledgement relay between said acknowledgement relay and said source of energizing potential and including a parallel circuit arrangement of said acknowledgement switch, a set of normally-open contacts of said alarm relay and a set of normally-open contacts of said acknowledgement relay in series circuit relation with said acknowledgement relay, whereby closure of any of said parallel connected elements will energize said acknowledgement relay, said energization circuit further including rst and second alternate branch circuits in series with said acknowledgementrelay and said parallel circuit, one of said branch circuits including normally-open contacts of said alarm relay in series with said alarm light which, when the variable being monitored is abnormal, effect the energization of the acknowledgement relay and the dim lighting of said alarm light, and, when said variable is abnormal or said alarm light burns out, effect the deenergization of said acknowledgement relay, the other branch circuit including normally-closed contacts of said alarm relay effecting energization ofthe acknowledgement relay when an abnormal condition of the variable has been acknowledged by momentary closure of said normally-open acknowledgement switch, an energization circuit for said alarm light including normally-closed contacts controlled by said alarm relay which connect the alarm light to said source of energizing potential to light the same brightly when the alarm relay becomes de-energized as the variable being monitored becomes abnormal, and an energization circuit for said trouble-indicating light includingsaid sensor switch, a set of normally-closed contacts of said acknowledgement relay and circuit connections connecting said sensor switch, trouble-indicating light and said latter contacts to .said source of energizing potential for lighting brightly said trouble-indicating light when the sensor switch is closed indicating a normal variable and said acknowledgement relay is de-energized.

12. An Vannunciator system comprising: a source of energizing potential, an alarm relay having sets of both normally-open and normally-.closed contacts, an acknowledgement relay having sets of both normally-open and normally-closed contacts, a normally-.closed sensor switch which `opens when the variable, to be monitored becomes abnormal, a normally-open acknowledgement switch, an alarm light, means connecting said alarm relay and said sensor switch in `series across said 4source of energizing potential, the alarmrelay thereby being normally energized, an energization circuit for said acknowledgement relay between said acknowledgement relay and said source of energizing potential and including a parallel circuit arrangement of said acknowledgement switch, a set of normally-open contacts .of said alarm relay and a set of normally-open contacts of said acknowledgement relay in seriescircuit relation with said acknowledgement relay, wherebyfclosureof any of said parallel connected elements will energize said acknowledgement relay, said energization circuit further including rst and second alternate branch circuits in series with said acknowledgement relay and said parallel circuit, one of said branch circuits including normally-,open contacts of said alarm relay in series withsaid alarm light which, when the variable being monitored is abnormal, effect the energization of the acknowledgement relay and the dim lighting of said alarm light, and, when said variable is abnormal or said alarm light burns out, effect the deenergization of said acknowledgement relay, the other branch circuit including normally-closed contacts of said alarm relay effecting energization of the acknowledgement relay when an abnormal condition of the variable has been acknowledged by momentary closure of said Y normally-open acknowledgement switch, `and an energization circuit for said alarm light including normally'- closed contacts controlled said alarm relay which connect the alarm light to said source of energizing potential to light the same brightly when the alarm relay becomes cle-energized as the variable being monitored becomes abnormal.

13. An annunciator system comprising: a source of energizing potential, an alarm relay, an acknowledgement relay, a normally-closed sensor switch which opens when the variable to be monitored becomes abnormal, an acknowledgement switch, a normally-open test switch, an alarm light, a test light, means connecting said alarm relay and said sensor switch in series across said source of energizing potential, the alarm relay thereby being normally energized, an energization circuit for said acknowledgement relay between said acknowledgement relay and said source of energizing potential and including a parallel circuit arrangement of said acknowledgement switch, a set of normally-open contacts of said alarm relay and a set of normally-open contacts of said acknowledgement relay in series circuit relation with said acknowledgement relay, whereby closure of any of said parallel connected elements will energize said acknowledgement relay, said energization circuit further including lirst and second alternate branch circuits in series with said acknowledgement relay and said parallel circuit, one of said branch circuits including normally-open contacts of said alarm relay which, when the variable being monitored is abnormal, eects the energization of the acknowledgement relay, and, when said variable is abnormal or said alarm light burns out, effects the deenergization of said acknowledgment relay, the other branch circuit including normally-closed contacts of said alarm relay effecting energization of the acknowledgement relay when an abnormal condition of the variable has been acknowledged lby momentary closure of said normally-open acknowledgement switch, an energization circuit for said alarm light including contacts controlled said alarm relay which connect the alarm light to said source of energizing potential to light' the same brightly when the alarm relay becomes de-energized as the variable being monitored becomes abnormal, andan venergization circuit for said test light comprising a series circuit of said sensor switch, normally-open test switch, a set of normally-open contacts ofv said acknowledgement relay, and 'said source of energizing potential, whereby the test light will become energized upon closure of said test switch provided'said acknowledgement relay is energized.

References Cited in the file of this patent UNITED STATES PATENTS.,

1,580,313 Mclntire Apr. 13, v1936 2,709,250 Marmorstone May 24, 1955 2,730,702 Marmorstone Jan; 10, 1956 

